Where did the OP go? The article loses on its first claim. It is not scientific, it is just an empty ignorant claim that ignores how mountains are made.
But since the OP is not here let me deal with fossil shells high up on mountains. Yes, we do observe that. Is it evidence for a flood? Not at all since they never made a testable hypothesis. But lets see what a testable hypothesis would look like.
If there was a global flood as in the Bible that would kill almost all sea life. Perhaps the larval stages of corals, mollusks etc. could survive. but the adult forms would have been killed by the changing salinity of sea water. Ask anyone that has a salt tank what happens to their pets if the salinity varies greatly. So we have a layer of dead sea life. And I suppose that some of it could be piled up on mountains, but one would need to explain how. Letting all of go what would we see? Well, at any one time there are not all that many clams, mussels, fish, or corals living. And the Earth was only a two or three thousand years old according to the myth. That does not give much time for the accumulation for much in the way of shells. So we might have a foot or two, heck call it three feet or even ten feet of shells built up by then, but that would be a huge exaggeration. What would we see Well we might have a few feet of shells that somehow survived extremely rough seas. What do we see instead. We see layers of limestone, sometimes thousands of feet thick when we add up all of the strata. Not just on mountains, but all around the world. Sorry, but the observations do not match the hypothesis. That claim is busted.
All that article is is a long list of PRATT's. If you are unfamiliar with that term it is an acronym. The letters stand for Points Refuted A Thousand Times.
If you want to find evidence for the flood you need to work a lot harder. Meanwhile here is a picture that drives Flood believers nuts. It is easy to explain with standard geology. It cannot be explained by relying on a worldwide Flood:
It is better if you go to the site. Left click on the image once. Then click on it again:
en.wikipedia.org
Wow! You can now click on it three times. But that is too much.